The A-Z of swimming pool jargon

swimming pool jargon
Share on facebook
Share on twitter
Share on linkedin
Share on google
Share on email

Confused by all the swimming pool jargon?

Who here knows the difference between pH and Total Alkalinity? No! Don’t worry. 

With everything there is to know about pools it can get confusing. 

When I first started at Eagle Leisure I had very little (if any) knowledge of swimming pools and how they worked. So the last few years has been spent furiously swotting up on all the pool chat. 

If you own a swimming pool. Or if you’re thinking about installing a swimming pool. There might be a lot of words and swimming pool jargon that doesn’t mean much. So here are some of the things I’ve learnt over the past few year. To help you get an understanding of all things swimming pools. 

Acidic water (low pH)

hot tub manufacturers

Acidic water is one of two sides of the pH scale. High acidity levels in the water, causes a low water pH. This will cause the water to become corrosive, which can irritate the skin and damage pool components.

Acidic water also can also cause sanitisers (a.k.a Chlorine) to break down faster than normal. This will mean you will have to put more chemicals in. Which, will result in you spending more on your pool running costs than necessary.

Acid (pH minus)

If your water pH is too high (above 7.8), then you will need to bring it down between 7.2-7.8. To do this, you will need to use an acid. The chemical used is Sodium Bisulphate, which is commonly referred to as pH minus.

Air handling unit

For an indoor pool, not only do you need to heat the pool. But you need to control the temperature of the pool hall and remove moisture from the air. An air handling unit takes care of all three.



Algae is a living organism that in the right conditions (out of balance water, warm water, sunlight, nitrates or CO2, poor circulation or poor filtration), can rapidly grow. Not only does your pool quickly turn a lovely uninviting shade of green. But it can consume Chlorine, causing you to use much more than necessary. And clog up your filtration system. All leading to a very unclean looking pool, that can be a haven for bacteria to grow.



Algaecides are what we use to prevent and kill algae. We recommend using a multifunctional Chlorine product which contains a preventative algaecide as part of your regular water maintenance. If you already have algae growth then you will need to use a product to kill the algae alongside shocking your pool with Chlorine.

Alkaline water

hot tub water and jets

Alkaline water is the other end of the pH scale. A high pH (above 7) dictates alkaline water.

A high pH can irritate your skin and eyes. Cause the water to be cloudy. And cause sanitisers to be up to 85% less effective. Meaning you will have to add more Chlorine to do the same job it would do in a balanced pool or hot tub.

Alkali (pH plus)


If your pool water is too acidic (low pH), then you will need to raise it to within 7.2 – 2.8. To do this you will use an alkali. This is known under the chemical name of Sodium Carbonate, and commonly called pH plus.


hot tub bacteria

E. Coli, Shigella, cryptosporidium and legionella. They are just some of the bacteria that can make a home in your swimming pool if the filtration and sanitiser levels are not maintained.

If these are not controlled and killed, they can lead to water-borne diseases and illnesses and even death. So water cleanliness needs to be a top priority when designing and maintaining your pool.



In order to increase the efficiency of your swimming pool filter, it will require regular backwashing.

This should be done weekly. It involves reversing the flow of pool water through the pool filter to remove any contaminants caught in the filter.


Related content:

Balanced water

The interaction of different water chemistry factors to create the correct mineral and pH content required to minimise corrosion and sale formation.

These factors include pH; temperature; hardness and total alkalinity.


Back to the top 


An alternative to Chlorine for killing the bacteria in a pool.

Chlorine is most often used as it is the cheaper and more familiar product.

However, Bromine has a number of advantages. It can be less irritating to the eyes. It remains effective in an unstable pH. And, Bromine remains effective in it’s combined form, unlike Chlorine.

Bromine should be 4-6mg/l in business use. And 2-4mg/l in domestic use.

Calcium hardness

Calcium Hardness is the measure of how hard or soft your pool water is. Or in other words, how much calcium is dissolved in your water.

In Scotland, we have soft water (low calcium levels). So we need to ensure calcium is kept high enough that it does not become corrosive and draw calcium from the metals, tile and grout in the pool.

In cases of areas with hard water (high calcium deposits), it needs to be balanced to ensure Calcium Carbonate (scale) does not form.

Ideal calcium levels are between 75 – 500mg/l.

Calcium hardness raiser

In Scotland, we may need to raise the level of calcium in the water. Water is naturally calcium seeking, so if there is none in the water it will draw calcium from available sources including tile grout and metals. To raise the calcium to the idea of 200mg/litre we use Calcium Chloride, commonly known as calcium hardness.


jacuzzi hot tub error messages

Chemical free is the dream. But sadly it’s still just that.

Secondary sanitisation systems such as ozone and UV systems can reduce the need for Chlorine or Bromine. But the use of either one of these is still necessary for both commercial and domestic pools to kill bacteria.

Related content:


Chlorine is still the most common pool disinfectant. Its job is to kill bacteria and viruses in the pool water. 

Too much chlorine can irritate the skin, eyes and sinuses.

While too little can lead to a risk of waterborne disease. 

Closing the pool

In Winter time, especially in Scotland, you may need to “close down” or “Winterize” your pool. This involves shutting it off. But in a way that protects the pool shell and fittings from damage due to freezing water. 

Outside pools may be closed down (winterizing) for winter to protect it from damage due to freezing water.

Contact us for more information on how to do this.

Back to the top 


Pool covers help protect the pool from dirt and debris, which can impact on the level of Chlorine needed to keep the pool contaminant free. But, they also play a massive part in reducing energy usage and costs.

Cover range from the fairly inexpensive “bubble covers”. To the more expensive automatic covers. It’s worth discussing during installation what option best suits your initial budget and long-term running costs. Covers can be retrofitted if you don’t already have one.

Related content

Deck level pool

Deck level pools are regarded as the best circulation system. The water spills from the pool over into the surrounding channel. Before running through the pipework and balance tank, being filtered and returned to the pool water. 

Deck level pools are usually more expensive to construct that skimmer pools. Due to the inclusion of a balance tank. 

The traditional means of covering the channels in deck levels pools are using plastic grating. However, for modern or high-end builds there are alternatives such as stone grating or stone


Have you got condensation on your windows? A dehumidifier will help remove condensation and increase ventilation. Without removing the heat from the room. Making it an efficient means of removing moisture from the swimming pool hall.

DIY pool build

Do you want to build your own pool?

We often work alongside construction companies or self-build projects on a supply only or consultation basis. 

You can build your own pool. Just remember it’s not a case of digging a hole and putting some water in it. There are several technical and safety aspects you need to take into consideration. But that’s where we can help. 

If you need supply or consultation advise on a DIY pool build give us a call.

Dosing unit

Swimming pools often use an automatic dosing system. This is a requirement in commercial properties. But they are often used in domestic pools as well to make the ongoing maintenance a bit easier.

Dosing units control the Chlorine levels and pH. They test the water, and when the ph or Chlorine levels move out with the set point they dose accordingly. We always recommend these even in domestic pools to reduce the time spent worrying about maintaining the pool. And increase the time you spend using it.


glass swimming pool filter

Filtration systems are the cleaning system of the pool. They “catch” dirt and debris and stop it floating back into the water. 

You can use sand, glass or OC-1 filter media within the filter, all to varying degrees of efficiency.

Related content:


Sometimes we get really, really tiny particles that even the filter can’t catch.

To solve this problem we use a flocculant. This binds together all the really tiny particles. Making them big enough for the filter to capture them.

Back to the top 

Liner Pools

Liner pools are increasing in popularity due to their lower cost. Faster installation. Easier maintenance. And with ever progressing liner designs, you might not even know its a liner pool.

Pools with liners usually have a base of either block work or steel panels. 

You can get different thicknesses of the liner. And the liner should last between 7-15 years depending on the type and how well it is cared for.

Related content:

Opening the pool

Once your pool is up and running you’re going to need to keep on top of maintenance. 

This can range from checking the chemicals are correct in the water. Backwashing the filter. Cleaning the skimmer. And checking the equipment to flag for any potential problems.

This is all entirely possible yourself. But it is necessary. We find that customers who invest in ongoing maintenance have less unexpected repairs. Therefore saving money and stress in the long run.


If you close your pool for the Winter. Then you will need to open it again. Usually around March/April. 

The pool is re-commissioned and a service is carried out to check everything is running as it should for the swim season ahead.

One-piece pools

One-piece pools are exactly what they say on the tin. They are pools that arrive in one piece. With pool shell, skimmers, underwater lighting and anything else you want on it pre-assembled at the factory to meet your specifications.

These are fast to install. And easy to maintain. So are increasing in popularity.

For more information on everything to do with one-piece pools visit River Pools.

Related content:

Ozone sanitation system

Contrary to what some salespeople might tell you. Ozone is not a replacement for Chlorine or Bromine. But it will help you reduce the use of them.

All pools and hot tubs need primary sanitisation systems (Chlorine/Bromine). But a secondary sanitisation system such as an ozone system will help reduce the number of chemicals needed. 

Ozone systems use O3 (ozone gas) to sanitise pool and hot tub water. They are installed within the pipework of a hot tub, or in the plant room of a pool. 

pH level

The pH level runs from 0-14. With 0-6.9 being acidic. 7 neutral. And 7.1-14 alkaline. 

pH affects the comfort level of the bather. It dictates the level of the corrosiveness of the water. Plus, it affects the ability of sanitisers to do their job. So it is arguably the most important factor when it comes to water maintenance. 


This is the room where all the pool equipment eg. filter, pumps, dosing panel etc are located. 


Stagnant water is a pool and hot tubs enemy and bacterias friend. We always want to keep the water circulating through the filtration systems. This is where the pumps come into play.

The pumps pull water from the suction ports (eg. skimmer/main drains), push it through the filter and heater. And then put it back into the pool. The pump allows the water to remain clean.

Pool hall

The area where the pool is located, in a commercial or private property. Often this includes a Sauna; Hot Tub or Steam room.

Back to the top


A primary sanitiser is necessary for your pool to kill contaminants such as bacteria and viruses. Chlorine and Bromine are the most commonly used and recommended sanitisers. 

Shock treatment

This is often referred to as ‘oxidising’ the water.

Once the Chlorine has done its job and attached to the contaminants in your pool. It becomes dead Chlorine. 

This is where shock treatments come in. You need to oxidise this dead Chlorine off. 

You do this by rapidly increasing the Chlorine levels, which will remove the redundant Chlorine and kill off resistant bacteria.


A pool skimmer helps clean the water by drawing in water, and capturing debris before it can sink to the bottom of the pool.

Most skimmers are built into the upper sides of the pool. 

They are usually accessed via the pool deck area through a trap door or hatch for cleaning.

Skimmer pool

In a skimmer pool, the water will sit approximately 6″ below the surrounding deck. The skimmer/s are fitted to the walls of the pool and they continuously ‘skim’ water off the top of the water to keep the surface clean.

SPATA (swimming pool & allied trade association)

Swimming Pool & Allied Trades Association, the governing body for the UK pool and spa industry. Eagle Leisure is a member of SPATA

Visit the SPATA website to find your local certified swimming pool installer.

Sprayed concrete pool

Do you want the strong man of swimming pool construction? 

You want a sprayed concrete pool. Not only are they the strongest type of construction. But they are fully customisable. Any shape you can imagine. Your pool can be built as.

Because of this, they are the most expensive type of pool.

Related content:


In order to check that your pH and sanitiser (among other things) are correct, you need to test the pool water. 

There are a few ways to do this. You can use an electronic test kit. Test Strips. Or pool testers. 

For domestic pools, we would usually recommend a pool tester. Otherwise, you can invest in an electronic pool tester. 

Back to the top

Total alkalinity

It can be confusing. Total Alkalinity is not the same as alkalinity on the pH scale.

Why not just call it something different I know.

But total alkalinity is the measurement of the alkaline materials present in the water.

What does it mean for you?

If your total alkalinity is not within the recommended levels of 80-160mg/litre you will find it’s difficult to balance the pH.

Low will cause an easy shift in pH, plus corrosive water. And high TA will make it very difficult to get any movement in pH, and you will need to use a lot of chemicals to correct the pH.

TA raiser

If you find you need to raise the total alkalinity then you will need to use TA raiser, which uses the chemical Sodium Bicarbonate.

This has the pH of around 9. So if you find both your pH and TA are low. Then you can use TA raiser, which will naturally bring both up and help to stabilise the TA.

Ta reducer

The opposite of TA Raiser. This will lower the total alkalinity of the pool water. 

Ultraviolet sanitisation system

UV light systems are another option for secondary sanitisation systems. The UV light disrupts or destroys organisms such as algae, bacteria and viruses.

Again, it still needs to be used alongside Chlorine or Bromine for effective disinfection.


Pool vacuums are used to rid the pool of dirt and debris that has not been removed by the filtrations system. Either as it is too big to be pulled into the suction system. Or because it has fallen to the bottom of the pool.

We love the Dolphin pool cleaner which automatically trails across both the bottom and sides of the pool.

Back to the top 

In summary

This is by no means an exhaustive list. But it’s hopefully going to help you get to grips with everything that is part of your pool and plant room.

If you think of any that we have missed off let us know and we will get them added.

Debbie Ekins
Debbie Ekins
Eagle Leisure - Sales & Marketing Manager Mission = to arm you with the knowledge you need to make the best buying decisions. Fuelled by coffee (and naps). Explorer of Scotland and the world.
Share on facebook
Share on twitter
Share on linkedin
Share on google
Share on email